Why won BAPI transactions work with the SAP LOB activity?
The BAPI call and the commit call must use the same underlying LOB connection. WF doesn’t currently support session scope. To work around this behavior, write a custom code activity that invokes both calls from the same proxy instance. For more information about invoking BAPI transactions from a Workflow see the blog post Invoking BAPI Transactions from a Workflow (http://blogs.msdn.com/b/biztalk_server_team_blog/archive/2010/07/06/handling-of-bapi-transactions.aspx).